Extrusion dies operating under high pressure often experience a significant amount of distortion. This observed distortion can be particularly prevalent when extruding viscous fluids through relatively wide die cavities having narrow internal flow channels. Such distortion can significantly affect the cross-sectional thickness profile of the extruded material upon exiting the die, which can result in undesirable variations in the extruded sheet.
The design of dies to overcome such deflection has been challenging, particularly when using predictive simulations. For many dies, there is a consistent discrepancy between simulated calculations of the cross-sectional flow profile and the actual, measured cross-sectional flow profile of a die as viscous fluids flow through an extrusion die. The discrepancy becomes more pronounced as the width of the die increases compared to the die body thickness. Prior art simulation models using either conventional Power-law fluid model, or even the more complicated Herschel-Bulkley model and thixotropic models do not resolve this observed discrepancy. As a result of the discrepancies between the simulated and measured values, the prior art simulation methods have been unsuccessful at providing optimized solutions to determine die cavities for uniform thickness extrusion.